There is an ongoing demand for smaller, thinner camera modules for use in cellphones and other electronic devices. Image sensors in the camera modules require miniaturization of pixels as well as an increase the number of pixels to achieve this smaller size while maintaining high-resolution in the image sensor. However, as pixel size decreases, the signal-to-noise ratio (SNR) becomes problematic, since signal attenuation increases when there is a decrease in light being available to the individual smaller pixels.
In some conventional image sensors, color images are produced using interpolation techniques that approximate colors in the produced image. However, the interpolation of colors may result in lower effective resolution. In other conventional image sensors, multiple dichroic mirrors are placed in the path of incident light, which results in enhanced color sensing by the image sensor. However, these types of image sensors are very expensive to manufacture. Additionally, the wavelength characteristics of the dichroic mirrors largely depend on the incidence angle of incoming light, which may cause the half wave length in the spectral characteristic to shift by several tens of nanometers due to a difference between the actual and expected light incidence angle. The difference in the spectral characteristics is further exaggerated because the dichroic mirrors have different characteristics when processing different wavelengths, which causes a degradation of the color reproduction. In addition, due to light polarization in the dichroic mirror, the transmission and the reflection characteristics differ greatly due to the presence of parallel (P) waves at the incident surface and perpendicular (S) waves at the incident surface. The presence of these waves causes the color separation characteristics to degrade.
What is needed is an image sensor having greater color sensitivity and improved optical efficiency.